Map table: for example have a table that can be interacted with by players, that way anyone can update it when they get back from exploring, this way it's more fun and interactable in-game instead of just always showing/updating where players have been, it would add a little more immersion to the game. (have a side option for markers as i understand if people want to keep/have their own markers and still explore areas themselves)
(or make a change in-game that registers all locations similar to how the trader is marked on your map, so when you find a place it will register on your map automatically and if you have completed a dungeon it will auto mark with an "X" on the map)
Lockers/cupboards/wardrobes for storage: similar to chests but larger and look way better, must be made from fine wood and maybe have more storage capacity.
character customization bench: it would require steel and fine wood to craft and you can change your hair and beard with some type of steel shaving kit.
Drawbridges: two sizes, one small one a little larger than a single wagon and a large one that can easily fit two wagons side by side. (obviously for traffic reasons) (would need chains, core wood, and fine wood to build for example)
Emote wheel: I believe the devs are already working on this obvious feature so there isn't much to say about it really, a simple press and hold options wheel, logical.
first-person mode/option: this one I'm still on the fence with because it may change the game too much but it could be a cool way to play. (blocking for example would be interesting with large shields as it would completely block your sight)
square options for manipulation tools: working next to buildings more easily and less accidental grass or terrain in your buildings.
that's all I can think of for now so feel free to share your ideas below, please try to keep ideas logical for the game and gameplay.
Source: https://www.reddit.com/r/valheim/comments/lyok3p/valheim_ideas_for_ingame_not_mods/